1. Field of the Invention
The present invention relates to a charged particle beam writing method and a charged particle beam writing apparatus, for example, an electron beam writing apparatus which uses a deflector to deflect an electron beam.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process which uniquely generates a pattern in semiconductor manufacturing processes. In recent years, with high integration of an LSI, a circuit line width required for semiconductor devices progressively decreases year after year. In order to form a desired circuit pattern on the semiconductor devices, a high-definition original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam writing technique has an essentially excellent resolution and is used in production of a high-definition original pattern.
FIG. 13 is a conceptual view for explaining an operation of a conventional variable-shaped electron beam photolithography apparatus.
In the variable-shaped electron beam photolithography apparatus (electron beam (EB) writing apparatus), writing is performed as follows. An opening 411 having a rectangular shape, for example, a square shape to shape an electron beam 330 is formed in a first aperture 410. A variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 in a desired square shape is formed in a second aperture 420. The electron beam 330 irradiated from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector. The electron beam 330 is irradiated on a target object 340 placed on a stage through a part of the variable-shaped opening 421. At this time, the stage continuously moves in one predetermined direction (for example, defined as an X direction). More specifically, a square shape which can pass through both the opening 411 and the variable-shaped opening 421 is written in a writing region of the target object 340. A scheme which causes an electron beam to pass through both the opening 411 and the variable-shaped opening 421 to form an arbitrary shape is called a variable-shaping scheme.
In general, overall control of electron optics of an electron beam writing apparatus is performed every shot which irradiates the electron beam 330 on the target object 340. More specifically, upon completion of irradiation of one shot, the next shot is prepared. The next shot is performed. In the electron beam writing apparatus, the electron beam 330 reaches the target object 340 while being deflected by a plurality of deflectors. In this case, upon completion of one shot, a period for preparing amplification to apply a voltage to the deflectors is necessary as a preparation period (so-called settling time) for the next shot.
As a technique related to the settling time, a technique which matches settling time to the longest preparation period of amplification is disclosed in a reference (for example, see JP-A-63-92020).
With an increase in degree of integration density of an LSI, time required for writing a mask by an electron beam writing apparatus or direct writing time required when writing is directly performed on a wafer or the like explosively increases. In order to cope with this, a current density of an electron beam used in the writing apparatus must be increased, or a device to shorten settling time between shots is required. In this case, as described above, in a conventional method, preparation for the next shot is performed upon completion of irradiation of one shot. In this method, the system has limitations even though irradiation time is shortened by increasing a current density of an electron beam and settling time is shortened by improving the capabilities of amplifiers for deflectors. For this reason, it is difficult to further shorten the writing time.